1. 1 Stage Detectors

• 2 stage detectors are slow since they require a 2 steps

1-1. 1 stage detectors

• simultaneous localization and classification
• Simple design
• Real-time detection
• Background error $\downarrow$

2. YOLO v1

• R-CNN : input → find region → classification, localization
• YOLO : input → find region, classification, localization

2-1. Pipeline

• $S*S$ Grid

• For each grid, compute $B$ bounding box and confidence score

  • confidence = $Pr(object) * IOU(truth pred)$

• For each grid compute $C$ class score

  • conditional class probability = $Pr(class_i|Object)$

  

• 1~5 : fist bounding box info